Process of impregnating fiber board with alpha salt



Patented Oct. 3, 1933 PATENT OFFICE PROCESS OF IIHPREGNATING FIBER BOARD WITH A SALT Alexander Winogradow, New York, N. Y.

No Drawing. Application October 8, 1931 Serial No. 567,769

7 Claims.

This invention relates to a process for impregnating with chemicals for the purpose of fireproofing fiber board having the characteristics of such products bearing the trade-names of Celotex, Nu-wood, Maftex, Vazcane and Insulating Board. These contain wood fiber obtained from various sources such as wood pulp, the fibers of the roots of licorice, and sugar cane. This type of board is light and porous, elastic and 10 readily compressible. The impregnation may have other uses than fireproofing, such as stifiening the board.

This material is' impregnated, according to the present invention, by causing to be formed in it a salt, such as mono-ammonium phosphate or di-ammonium phosphate. Impregnation with either or both of these salts will fireproof the board.

The process consists essentially in causing an alcohol solution of an acid to impregnate the fiber board, and then to squeeze the board to get rid of the excess solution and to make it porous for the reception of ammonia gas, which is then applied until no more is absorbed. An ammonium salt is then formed in the board which is insoluble in alcohol. The board is then dried, by forced drying or just letting it stand till dry.

It is one of the advantages of my process that the salt is uniformly distributed throughout the mass of the board. Attempts heretofore made with fiber board by causing a water solution of the salt to impregnate the material and then letting it dry give poor results as the salt does not crystallize out uniformly through the material,

and a heavy crust of the salt usually is formed on the surface.

The squeezing, as used in my process, causes a more complete distribution of the solution in the board than otherwise, and it also gives a porosity in the solution soaked board, by forming air pockets, for the ready entrance and distribution of the ammonia gas. The squeezing removes a portion of the solution that has already penetrated the board. It takes into account the elastic properties of the board. The board which is impregnated throughout its mass is squeezed to reduce it in volume temporarily so as to remove a large proportion of its solution. This reduces the amount of alcohol to be evaporated in the drying step.

The amount of the pressure used in squeezing should be such that the board is not crushed and its characteristics impaired. It should be within the elastic limit of the material, that is such a 5 limit with this material, that said material will recover substantially its original volume in a reasonable time. Other processes, in which squeezing the fiber board is made use of in impregnating the board, are described in my copending applications, Serial Nos. 469,939 and 620,537.

Any acid soluble in alcohol will do which forms, upon the addition of ammonia, a salt which is insoluble in alcohol. Many organic solvents can be used such as methanol, ethyl alcohol and acetone in which the particular acid used is soluble and which forms, upon the addition of ammonia a salt insoluble in the solvent.

The fiber board is impregnated with the solution by being simply soaked therein or the solution may be forced in under pressure, or the board placed in a container with the solution and the saturation. The ammonia gas is applied with or without pressure.

As a particular example of my process, a one pound board celotex, one-half inch thick is impregnated with a 15 per cent solution of phosphoric acid in ethyl alcohol. The board is then squeezed by rolls or plates to prepare the porosity for the ammonia, and to get rid of the excess mixture. Ammonia gas is then applied until no more is absorbed, forming, throughout the board, an ammonium phosphate salt, which is insolubl lnalcohol. The board is then dried.

As another example, the board can be fireproofed by using a solution of hydrochloric acid, HCL, in methyl alcohol, to impregnate the board. After squeezing, the board is subjected to the ammonia as before and then dried. The fireproofing salt formed in this example is NH4CL, ammonium chloride.

The term alcohol as used in the claims is intended to cover the broader meaning of an organic solvent as defined above. The term fiber board as used in the claims is intended to have the meaning as given hereinbefore.

I claim:-

1. The process of impregnating fiber board with a salt consisting in impregnating said board with an alcohol solution of an acid which upon the addition of ammonia forms a salt insoluble in alcohol, then squeezing said board'to remove a portion of said solution, then applying ammonia to the board for the formation oi! said salt throughout the board, and then drying the board.

2. The process of impregnating fiber board with a salt consisting in impregnating said board with an alcohol solution of an acid which upon the addition or ammonia forms a salt insoluble in the alcohol, then squeezing said board up to substantially its elastic limit, then applying ammonia to the board for the formation of said salt throughout the board, and then efiecting the drying of the board.

3. The process of impregnating fiber board with a salt consisting in completely impregnating said board by immersing it in an alcohol solution of an acid which upon the addition of ammonia forms a salt insoluble in the alcohol and then subjecting said solution to a pressure otli'e'rthan atmospheric, removing a portion of said solution from within the board by squeezing said board, then applying ammonia to the board for the formation of said salt within the board, and then drying the board.

4. The process oi impregnating fiber board with a salt consisting in impregnating said board with an alcohol solution of an acid which upon the addition oi ammonia forms a salt insoluble in the alcohol, removing a portion of said solution from within the board by squeezing said board, then forcing ammonia under pressure into said board for the formation of said salt in the board, and then effecting the drying of the board.

5. The process of fireproofing fiber board consisting in impregnating said board with a solution of phosphoric acid in alcohol, then removing a portion of said solution from within the board by squeezing said board, then applying ammonia to the board for forming an ammonium phosphate salt in the board, and then effecting the drying of the board.

6. The process of fireproofing fiber board consisting in impregnating said board with an alcohol solution of an acid which upon the addition or ammonia formsa salt insoluble in alcohol, then removing a portion of said solution from within the board by squeezing said board, then saturating said board with ammonia and then drying the board.

7. The process of impregnating fiber board with a salt consisting in impregnating said board with an alcohol solution of an acid which upon the addition of ammonia forms a salt insoluble in the alcohol, then squeezing said board after being removed from the solution with sufficient pressure to reduce its volume enough to effect the removal from within the board of enough solution to effect the formation of air pockets in the board, then applying ammonia to the'board for then drying the board.

ALEXANDER WINOGRADOW. 

